It has been customary to use a slurry method to form fluorescent screens of cathode-ray tubes for television receivers, display devices for use with computers and the like. A fluorescent screen of a color cathode-ray tube, for example, is formed as follows.
First, a photosensitive painted film is formed on a panel of a cathode-ray tube, i.e. the inner surface of a panel having a skirt portion extended over the whole of the peripheral edge portion. Photosensitive painted films such as PVA (polyvinyl alcohol)—ADC (ammonium dichromate) based photosensitive painted films or PVA (polyvinyl pyrrolidone)—DAS (4,4′-diazitostilbene 2,2′-disulfuric acid ammonium) based photosensitive painted films are available as the above photosensitive painted film. After the photosensitive painted film has been dried, the dried photosensitive painted film is exposed with irradiation of ultraviolet rays by using a color selection structure as an optical mask and developed by a suitable method such as rinsing by water, thereby resulting in stripe-like resist layers, for example, being formed at the positions corresponding to respective colors.
Next, after a carbon slurry has been coated on the whole surface including the resist layers and dried, the resultant product is treated by a reversal process, the carbon layer on the resist layers is removed by a lift off method in unison with the resist layers and thereby carbon stripes (CS) with predetermined patterns are formed.
Next, a fluorescent substance slurry of a first color, e.g. blue is coated on the carbon stripes. After the thus coated fluorescent substance slurry has been dried, the resultant product is exposed with irradiation of ultraviolet rays by using the color selection structure as the optical mask and then developed to form a blue fluorescent substance stripe between predetermined carbon stripes. In a like manner, a green fluorescent substance stripe and a red fluorescent substance strip are formed between other carbon stripes (CS) and thereby a desired color fluorescent screen is formed.
According to the above-mentioned slurry method, when the resist layer is processed, the panel of the cathode-ray tube has to be rotated. At that time, not only electric power is required but also a large amount of surplus resist stripper is scattered around the panel. As a result, treatment of the resist stripper that has been scattered around the panel and waste disposal of the surplus resist stripper need a large amount of cost and much time and labor. Moreover, much electric power is consumed to dry the carbon slurries that have been coated on the whole surface. In order to solve the above-mentioned problems and in order to simplify the manufacturing process of a color cathode-ray tube and to decrease electric power, so far there has been known a method of forming a fluorescent screen by a transfer method.
A fluorescent screen is formed by a transfer method as follows. A transfer sheet composed of at least adhesive layers and fluorescent substance layers and which is supplied from a supply reel and rewound by a take-up reel is overlaid on the inner surface (inner surface on which carbon stripes are formed) of the panel of a cathode-ray tube, and the transfer sheet is joined to the inner surface of the panel with application of heat and pressure with the transfer roller while the transfer roller rotatably moves over the inner surface of the panel from one end to the other end of the inner surface of the panel. After the transfer sheet has been joined to the inner surface of the panel, the transfer roller is released and the transfer film is stripped, whereafter a fluorescent substance layer of first color, e.g. green fluorescent substance layer is transferred to the whole surface of the inner surface of the panel. Thereafter, the resultant product is exposed with irradiation of ultraviolet rays by using a color selection structure as an optical mask, developed by a suitable method such as rinsing by water, and dried to thereby form a green fluorescent substance stripe. By similar methods, a fluorescent substance stripe of second color, e.g. blue fluorescent substance stripe and a fluorescent substance stripe of third color, e.g. red fluorescent substance stripe are formed, in that order.
However, according to the fluorescent screen forming method and fluorescent screen forming apparatus based on the conventional transfer method, because panel pins for supporting the color selection structure are protruded from the inner surface of the panel skirt portion, it is difficult to join the transfer film up to the end edges of the inner surface of the panel, and hence an effective display area (what might be called an effective screen) is limited unavoidably. On the other hand, it is desired that the transfer sheet can be transferred over the whole area of the inner surface of the panel including the end edges under uniform transfer pressure without fogging produced in the fluorescent substance layers and without wrinkles produced in the fluorescent substance layers at the corner portions.